Conservation of Linear Momentum AP Physics C Mechanics MCQ – Exam Style Questions etc.
Conservation of Linear Momentum AP Physics C Mechanics MCQ
Unit 4: Linear Momentum
Weightage : 15-25%
Question(a)-(b)are based on the following information.
Three identical spheres are thrown from the same height above the ground. Sphere X is thrown vertically up, sphere Y is thrown horizontally, and sphere Z is thrown vertically down, as shown in
figures 1, 2, and 3 above, respectively. All three spheres are thrown with the same speed. Air resistance is negligible.
Question(a)
Which sphere or spheres initially collide with the ground with the greatest speed?
(A) Sphere X only
(B) Sphere Y only
(C) Sphere Z only
(D) Spheres X and Z only
(E) All three spheres collide with the same speed.
Answer/Explanation
Ans:E
Question(b)
Assume the spheres collide elastically with the ground. Which of the following ranks the spheres based on the rebound height after they collide with the ground?
(A) X>Y>Z
(B) Y> (X => Z)
(C) Z>Y>X
(D) ( X =Y ) >Z
(E) (X= Z) >= Y
Answer/Explanation
Ans:E
Question
A 2 kg ball collides with the floor at an angle\( \theta\) and rebounds at the same angle and speed as shown above. Which of the following vectors represents the impulse exerted on the ball by the floor?
Answer/Explanation
Ans:E
Question
An astronaut in space accidentally becomes disconnected form her ship’s tether. In order to get back to safety, she throws a wrench of mass m = 2 kg directly away from the ship at a speed v = 30 m/s. Given that she has a mass of 60 kg and was at rest before throwing the wrench, how long will it take her to get back to the ship if she is 35m away from it?
(A) 60 s
(B) 45 s
(C) 35 s
(D) 25 s
(E) 15 s
Answer/Explanation
Ans: C
Use the Law of Conservation of Linear Momentum to determine how quickly she’ll move after throwing the wrench. We know the total momentum of the system must be o, so
\(0 = m_1 v_1 + m_2 v_2\)
\(m_1 v_1 = m_2 v_2\)
\(v_1 = m_2 v_2 / m_1\)
=\([(2 kg)(30 m/s)]/(60 kg) = 1 m/s\)
If she moves at 1 m/s, it will take 35 s to get back to the shuttle.